In the description of the Chinook it says that if it is shot down all aboard are lost.
Why?
When I shoot down a UFO that's not the case. There's wreckage and survivors and gear leftover. What if the same happened when MY transport got shot down?
Okay, so I send out my Chinook full of my best commandos and gear. Blam. It goes down. Now I have the option of sending a second team in. When I make my landing I get a message telling me how bad the crash is and the likelihood of there being survivors.
Somewhere on the map is the shattered remains of my Chinook, along with scattered corpses, gear, incapacitated xenonauts, and perhaps even a few particularly resilient, albeit injured and outnumbered, xenonauts.
The alien craft that shot them down or perhaps a separate transport is there to finish off my xenonauts. I have to fight my way to them. I win if I retrieve all survivors, including unconscious xenonauts, and return them to my Chinook, or if I defeat all aliens.
Alternatively the Chinook is shot down and gone. There is a random chance that within the next few days a garbled message will be received from survivors of the lost team. This opens a rescue mission somewhere near the crash site. Wounded survivors are holed up somewhere and dangerously low on ammo, desperately fighting to hold off the alien onslaught.
I think it would be an interesting change up and I might be less inclined to immediately reload a saved game upon losing my Chinook. A mission like that would be too damn fun to miss out on.